Aerogel particle and method of producing the same

ABSTRACT

An aerogel particle is produced by following processes. A mixing process: an alkoxysilane compound is mixed with an organic solvent to form a first mixed solution. A hydrolysis process: an acid catalyst is added into the first mixed solution to perform a hydrolysis reaction, thereby obtaining a sol. A condensation process: an alkali catalyst is added into the sol to perform a condensation reaction, and a hydrophobic dispersion solvent is added and stirred during the condensation process, thereby subjecting sol to be gelled when it is stirred, further producing the aerogel particle with a uniform structure.

RELATED APPLICATIONS

This application claims priority to Taiwan Application Serial Number104116983, filed on May 27, 2015, which is herein incorporated byreference.

BACKGROUND Field of Invention

The present invention relates to an aerogel particle and a method ofproducing the same. More particularly, the present invention relates toan improved sol-gel method of producing an aerogel particle with auniform particle structure.

Description of Related Art

An aerogel is a porous material, which has a stereoscopic networkstructure and very low thermal conductivity rate. The aerogel isgenerally applied in thermal isolation materials.

Typically, the aerogel is produced by a sol-gel method. A precursor suchas alkoxysilane or methyl silicate is firstly mixed with an organicsolvent, and then an acid catalyst is added therein to perform ahydrolysis reaction. When the hydrolysis reaction is performed for agiven period of time, an alkali catalyst is added therein to perform acondensation reaction, thereby forming a gel during the condensationreaction gradually. Molecules in the gel are continuously condensed andbonded, so as to form a semisolid-state polymer gel gradually. The gelis aged for a given period of time and formed to a stably stereoscopicnetwork structure. Finally, the solvent such as water, methanol and thelike in the aerogel is extracted and dried by supercritical dryingtechnology, thereby obtaining a dried block of porous aerogel.

The supercritical drying technology used in the aforementioned methodcan prevent the aerogel from being broken by a surface tension of thewater under normal atmospheric pressure. However, the supercriticaldrying technology must be performed under high pressure, only a verysmall amount of the aerogel can be dried in each supercritical dryingprocess. Accordingly, it is hard to produce the aerogel in mass and toreduce the production cost of the aerogel.

On the other hand, during application, the dried block of the aerogelmust be crushed, but aerogel pieces crushed from the aerogel block byconventional methods generally have uneven structures and brokenappearances (please refer to FIGS. 9 to 12), so that such piecesunlikely possess excellent thermal isolation property.

Some prior art such as Taiwan Patent Publication No. 200835648 disclosesa porous material and a method of producing the same. Briefly, theporous material is synthesized by a sol-gel method, in which analkoxysilane or a silicate compound reacts in an organic solvent, andthe reactant is then modified by a modification agent for replacing ahydrophilic functional group on a surface of the porous material to ahydrophobic functional group, so that the porous material can beprevented from being broken by surface tension of the water. Therefore,the porous material can be dried at room temperature under normalatmospheric pressure.

The hydrophobic modification of the porous material of theaforementioned prior art is performed by multi-batch solventdisplacement technology at room temperature under normal atmosphericpressure. However, the hydrophobic modification must be performed formore than 24 hours at room temperature under normal atmosphericpressure. Thus, such hydrophobic modification does not meet the costefficiency due to too long processing time.

Moreover, when the aforementioned porous material is applied, the porousmaterial needs to be crushed. Therefore, pieces crushed from the porousmaterial also have defects of the uneven structures and the brokenappearances.

SUMMARY

Accordingly, in order to improve the defects of poor thermal isolationproperty due to the uneven structure and the broken appearances of theconventional aerogel, a method of producing the aerogel particle isprovided. The present method includes a mixing process, a hydrolysisprocess and a condensation process as follows. In the mixing process, analkoxysilane compound is mixed with an organic solvent to form a firstmixed solution. In the hydrolysis process, an acid catalyst is addedinto the first mixed solution to perform a hydrolysis reaction, therebyforming a sol. In the condensation process, an alkali catalyst is addedinto the sol to perform a condensation reaction, and a hydrophobicdispersion solvent is added and stirred during the condensationreaction. The sol is gelled when it is stirred, thereby producing asecond mixed solution including the aerogel particle.

Further, the hydrophobic solvent includes but is not limited to ketone,ether, ester, aromatic and alkane.

Yet further, after the condensation process is performed, the methodfurther comprises a post-treatment process subjected to the second mixedsolution. The aforementioned aerogel particle is filtered out by afilter and washed by a mixed solution including ethanol and water. Andthen, the aerogel particle is dried at 100° C. to 115° C. in vacuum.

Yet further, after the condensation process is performed, the methodfurther comprises a hydrophobic modified process subjected to the secondmixed solution. The second mixed solution is heated to evaporate theorganic solvent, and a chloryl organic molecule is added into the secondmixed solution, thereby subjecting the chloryl organic molecule to reactwith a hydroxyl group of the aerogel particle. Therefore, the aerogelparticle is hydrophobic, and the hydrophobic dispersion solvent canprevent the aerogel particle from being broken.

Yet further, the chloryl organic molecule can include but be not limitedto chloryl alkoxysilane, chloryl alkane and chloryl phene.

Yet further, the organic solvent includes a mixture of ethanol andwater. In the hydrophobic modified process, a temperature of the secondmixed solution is varied sequentially to a first temperature, a secondtemperature and a third temperature. The first temperature is 78° C. to82° C., the second temperature is 100° C. to 115° C., and the thirdtemperature is 40° C. to 45° C. When the temperature of the second mixedsolution is varied to the third temperature, the chloryl organicmolecule is added.

Yet further, after the hydrophobic modified process is performed, themethod further comprises a post-treatment process. The aerogel particleis filtered out by a filter and washed by toluene, and then the aerogelparticle is dried in vacuum.

The present invention also provides an aerogel particle. The aerogelparticle is produced by following processes. A mixing process: analkoxysilane compound is mixed with an organic solvent to form a firstmixed solution. A hydrolysis process: an acid catalyst is added into thefirst mixed solution to perform a hydrolysis reaction, thereby forming asol. A condensation process: an alkali catalyst is added into the sol toperform a condensation reaction. A hydrophobic dispersion solvent isadded and stirred during the condensation reaction. The sol is gelledwhen it is stirred, thereby producing the second mixed solutionincluding the aerogel particle. A particle size of the aforementionedaerogel particle is 300 nm to 900 nm.

The present invention has following effects:

1. In the condensation process of the method of producing the presentinvention, the aerogel particle is stirred in a large amount ofnon-dissolved solvent, thereby producing uniform pearl-like structureaerogel particle with better thermal isolation, further therebyenhancing the practicality of the product.

2. The porosity and the pore size of the aerogel particle can beadjusted by the parameters of the method, such as an amount of thesolvent, a viscosity of the solvent, an amount of the acid catalyst andan amount of the alkali catalyst.

3. The processing time of the aerogel particle can be controlled byadjusting the amount of the alkali catalyst.

4. A size of the sub-micro pearl-like aerogel particle can beefficiently controlled by adjusting the amount of the non-dissolvedsolvent and a stirring velocity. When the amount of the non-dissolvedsolvent is higher and the stirring velocity is faster, the size of theaerogel particle is smaller; relatively, when a viscosity of thenon-dissolved solvent is lower and the stirring velocity is slower, thesize of the aerogel particle is larger.

5. The processing time of the displacement technology can be decreasedby controlling the temperature of the hydrophobic modified process. Thehydrophilic or hydrophobic aerogel particle can be continuously producedin 4 hours to 5 hours, thereby enhancing the producing efficiency of theaerogel particle.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the followingdetailed description of the embodiment, with reference made to theaccompanying drawings as follows:

FIG. 1 is a flow chart according to an embodiment of the presentinvention.

FIG. 2 is a flow chart with the modified process according to anembodiment of the present invention.

FIG. 3 is a scanning electron microscope picture of the aerogel particleof the present invention when the stirring velocity is 1200 rpm.

FIG. 4 is a scanning electron microscope picture of the aerogel particleof the present invention when the stirring velocity is 1800 rpm.

FIG. 5 is a transmission electron microscopy picture of the closed-shellaerogel particle of the present invention.

FIG. 6 is a scale-up picture of the transmission electron microscopy ofthe closed-shell aerogel particle of the present invention.

FIG. 7 is an absorbed curve diagram and a desorbed curve diagram of theaerogel particle without subjecting to the hydrophobic modified processin nitrogen gas.

FIG. 8 is a pore distribution diagram of the aerogel particle accordingto FIG. 7.

FIG. 9 is scanning electron microscope picture of a commercial aerogelpowder under a scaling factor 500.

FIG. 10 is scanning electron microscope picture of a commercial aerogelpowder under a scaling factor 1,000.

FIG. 11 is scanning electron microscope picture of a commercial aerogelpowder under a scaling factor 5,000.

FIG. 12 is scanning electron microscope picture of a commercial aerogelpowder under a scaling factor 10,000.

DETAILED DESCRIPTION

According to the aforementioned features, the effects of the aerogelparticle and the method of producing the same can be clearly showed byfollowing embodiments.

Please refer to FIG. 1, which discloses the method of producing theaerogel particle according to an embodiment of the present invention.The method comprises following processes: a mixing process (S1), ahydrolysis process (S2), a condensation process (S3) and apost-treatment process (S4).

The mixing process (S1): an alkoxysilane compound is mixed with anorganic solvent to form a first mixed solution. The alkoxysilane can betetramethoxysilane (TMOS), tetraethoxysilane (TEOS), or a precursor ofmethyl silicate or the like. An amount of the alkoxysilane or theprecursor of methyl silicate is 2.1 mol % to 12.5 mol %, and an amountof the organic solvent is 97.9 mol % to 87.5 mol %.

The hydrolysis process (S2): an acid catalyst is added into the firstmixed solution to perform a hydrolysis reaction, thereby forming a sol.A ratio of an amount of the alkoxysilane to an amount of the acidcatalyst is 1:0.3 to 1:0.001.

Besides, the ratio of the amount of the alkoxysilane to the amount ofthe acid catalyst is 1:0.001 to 1:0.3. When the ratio of the amount ofthe alkoxysilane to the amount of the acid catalyst is 1:0.001, theprocessing time of the hydrolysis reaction is 300 minutes. When theratio of the amount of the alkoxysilane to the amount of the acidcatalyst is 1:0.3, the processing time of the hydrolysis reaction is 10minutes. Accordingly, the processing time of the hydrolysis reactiondecreases as increasing of the amount of the acid catalyst.

The condensation process (S3): an alkali catalyst is added into the solto perform a condensation reaction. A molar ratio of a mole of a mixedsolution including the acid catalyst and the ethanol to a mole of amixed solution including the alkali catalyst and the ethanol is 10:10 to10:40. A molar ratio of a mole of the alkali catalyst to a mole of theacid catalyst is 1.0:1.0 to 3.0:1.0.

In the mixed solution including the alkali catalyst and the ethanol, acondensation reaction time (i.e. a gelling time of the aerogel) isdistinctly decreased as increasing the amount of the alkali catalyst.When the molar ratio of the mole of the alkali catalyst to the mole ofthe acid catalyst is 1.0:1.0, the gelling time essentially is 1600minutes. When the molar ratio of the mole of the alkali catalyst to themole of the acid catalyst is 3.0:1.0, the gelling time is decreased to 5minutes. Therefore, the processing time can be adjusted by controllingthe molar ratio of the mole of the alkali catalyst to the mole of theacid catalyst.

When the condensation reaction of the condensation process (S33)approximately complete, the first mixed solution that has been subjectedto the hydrolysis reaction (i.e. a mixed solution after hydrolysis) isformed to a sol. When the mixed solution after hydrolysis is controlledto a sol, a large amount of the non-dissolved hydrophobic dispersionsolvent is added into the sol to form a second mixed solution, and thesecond mixed solution is stirred at 1200 rpm to 2000 rpm. Accordingly,the sol is gelled, thereby forming a pearl structure or ball structureaerogel particle due to a repulsion of the hydrophobic dispersionsolvent under a fast stirring. A particle size of the aerogel particleessentially is 300 nm to 900 nm.

The aforementioned hydrophobic dispersion solvent can be ketone of 6 to16 carbons, ether of 6 to 16 carbons, ester of 6 to 16 carbons, aromaticof 7 to 16 carbons, alkane of 8 to 20 carbons, halogenated ether,halogenated ester, halogenated aromatic, halogenated alkane and thelike. For example, the hydrophobic dispersion solvent can be toluene,kerosene, cleaning naphtha or the like.

The post-treatment process (S4): the aerogel particle is filtered out bya filter, and the aerogel particle is washed by a mixed solutionincluding ethanol and water for 3 to 4 times. Then, the aerogel particleis dried at 110° C. to 115° C. in vacuum, thereby obtaining the aerogelparticle.

Please refer to FIG. 2, which is a flow chart with the modified processaccording to an embodiment of the present invention. Preferably, theaforementioned aerogel particle can further be subjected to ahydrophobic modified process. After the condensation process (S4) isperformed, the method can further comprise a hydrophobic modifiedprocess (S5) subjected to the second mixed solution. A temperature ofthe second mixed solution is sequentially varied to a first temperature,a second temperature and a third temperature. The first temperature is78° C. to 82° C., thereby evaporating the ethanol in the second mixedsolution (a boiling point of the ethanol is 78° C.). The secondtemperature is 100° C. to 115° C. (a boiling point of the water is 100 °C.), thereby evaporating the water in the second mixed solution. Thethird temperature is 40° C. to 45° C.

When the temperature of the second mixed solution is varied to the thirdtemperature, a chloryl organic molecule is added. The chloryl organicmolecule is selected from a group consisting of chloryl alkoxysilane,chloryl alkane, chloryl phene or a combination thereof.

Accordingly, the chloryl organic molecule is subjected to react with ahydroxyl group of the aforementioned aerogel particle, therebysubjecting the aerogel particle to be hydrophobic. Moreover, therepulsion between the hydrophobic dispersion solvent and the aerogelparticle can prevent the aforementioned aerogel particle from beingbroken. If the aerogel particle is subjected to the hydrophobic modifiedprocess (S5), the aerogel particle is washed by toluene in thepost-treatment process (S40) to remove the chloryl organic molecule. Andthen, the washed aerogel particle is dried in vacuum.

Therefore, the method of the present invention can produce the uniformsub-micro porous aerogel particle with ball structure. On one hand, themethod of the present invention can enhance the homogeneity of theappearances and the structure of the aerogel particle, therebyincreasing the applicability. On the other hand, the present method canproduce the hydrophobic modified aerogel particle by evaporating withheating and adding the chloryl organic molecule, thereby being easily tobe produced with a large amount, further thereby enlarging the appliedscope.

Please refer to the following Table 1, which shows a comparison of theaerogel particle according to an embodiment of the present inventionbetween before-modification and after-modification by a surface area andporosimetric analyzer (BET):

TABLE 1 S_(BET) V_(pore) D_(p) S_(micro) V_(micro) Sample (m²/g) (cm³/g)(nm) (m²/g) (cm³/g) Aerogel Particle (Before- 531 2.67 18.92 51 0.017Modification) Aerogel Particle (After- 784 3.42 16.28 42 0.021Modification)

In Table 1, S_(BET) represents a specific surface area measured by BET;V_(pore) represents a volume of the pore measured by BET; D_(p)represents a diameter of the pore measured by BET; S_(micro) representsa specific surface area of the micro pore; and V_(micro) represents avolume of the micro pore.

In Table 1, per unit weight of the before-modification andafter-modification aerogel particle are respectively measured by theBET. When the BET is vacuumed until P/Po is equal to 0, a nitrogen gasis introduced after the solvent or an absorbed impurity in the aerogelparticle is removed. When the aerogel particle absorbs the nitrogen gasuntil P/Po is equal to 1, the nitrogen gas is vacuumed to subject theaerogel particle with saturated nitrogen gas to be desorbed until P/Pois equal to 0. In the absorbed process and the desorbed process, theabsorbed curve and the desorbed curve are measured and analyzed, therebyobtaining the relative result of the specific surface area.

Please refer to FIG. 3 and FIG. 4, which are microscope pictures of theappearances and the structure of the aerogel particle by scanningelectron microscope in different scale. FIG. 3 and FIG. 4 show thestructure of the aerogel particle has uniform and high homogeneity ballstructure.

Please refer to FIG. 5 and FIG. 6, which are microscope pictures of theinner structure and the pore distribution of the aerogel particle byscanning electron microscope in different scale. FIG. 5 and FIG. 6 showthe aerogel particle is aggregated to form a nano-scale aerogelstructure.

Please refer to FIG. 7, which shows an absorbed curve diagram and adesorbed curve diagram of the aerogel particle without subjecting to thehydrophobic modified process in nitrogen gas. Please refer to FIG. 8,which shows a pore distribution diagram converted from the absorbedcurve diagram and the desorbed curve diagram of the aerogel particlewithout subjecting to the hydrophobic modified process.

As is understood by a person skilled in the art, the foregoing preferredembodiments of the present invention are illustrated of the presentinvention rather than limiting of the present invention. In view of theforegoing, it is intended to cover various modifications and similararrangements included within the spirit and scope of the appendedclaims. Therefore, the scope of which should be accorded the broadestinterpretation so as to encompass all such modifications and similarstructure.

What is claimed is:
 1. A method of producing an aerogel particle,comprising: performing a mixing process, wherein an alkoxysilanecompound is mixed with an organic solvent to form a first mixedsolution; performing a hydrolysis process to the first mixed solution,wherein an acid catalyst is added into the first mixed solution toperform a hydrolysis reaction, thereby forming a sol; and performing acondensation process to the sol, wherein an alkali catalyst is addedinto the sol to perform a condensation reaction, and a hydrophobicdispersion solvent is added and stirred during the condensation process,thereby subjecting the sol to be gelled when it is stirred, furtherproducing a second mixed solution including the aerogel particle.
 2. Themethod of producing an aerogel particle of claim 1, wherein thehydrophobic solvent is selected from a group consisting of ketone,ether, ester, aromatic and alkane.
 3. The method of producing theaerogel particle of claim 2, after the condensation process isperformed, the method further comprises: performing a post-treatmentprocess to the second mixed solution, wherein the aerogel particle isfiltered out by a filter and washed by a mixed solution includingethanol and water, and then the aerogel particle is dried at 100° C. to115° C. in vacuum.
 4. The method of producing the aerogel particle ofclaim 2, after the condensation process is performed, the method furthercomprises: performing a hydrophobic modified process to the second mixedsolution, wherein the second mixed solution is heated to evaporate theorganic solvent, and a chloryl organic molecule is added to subject thechloryl organic molecule to react with a hydroxyl group of the aerogelparticle, thereby subjecting the aerogel particle to be hydrophobic,further preventing the aerogel particle from being broken by thehydrophobic solvent.
 5. The method of producing the aerogel particle ofclaim 4, wherein the chloryl organic molecule is selected from a groupconsisting of chloryl alkoxysilane, chloryl alkane and chloryl phene. 6.The method of producing the aerogel particle of claim 4, the organicsolvent includes a mixture of ethanol and water; a temperature of thesecond mixed solution is sequentially varied to a first temperature, asecond temperature and a third temperature, wherein the firsttemperature is 78° C. to 82° C., the second temperature is 100° C. to115° C., the third temperature is 40° C. to 45° C., and when thetemperature of the second mixed solution is varied to the thirdtemperature, the chloryl organic molecule is added.
 7. The method ofproducing the aerogel particle of claim 4, after the hydrophobicmodified process is performed, the method further comprises: performinga post-treatment process, wherein the aerogel particle is filtered outby a filter and washed by toluene, and then the aerogel particle isdried in vacuum.
 8. The method of producing the aerogel particle ofclaim 1, wherein the sol is stirred at 1200 rpm to 2000 rpm when thecondensation process is performed.
 9. The method of producing theaerogel particle of claim 2, wherein the sol is stirred at 1200 rpm to2000 rpm when the condensation process is performed.
 10. The method ofproducing the aerogel particle of claim 3, wherein the sol is stirred at1200 rpm to 2000 rpm when the condensation process is performed.
 11. Themethod of producing the aerogel particle of claim 4, wherein the sol isstirred at 1200 rpm to 2000 rpm when the condensation process isperformed.
 12. The method of producing the aerogel particle of claim 5,wherein the sol is stirred at 1200 rpm to 2000 rpm when the condensationprocess is performed.
 13. The method of producing the aerogel particleof claim 6, wherein the sol is stirred at 1200 rpm to 2000 rpm when thecondensation process is performed.
 14. The method of producing theaerogel particle of claim 7, wherein the sol is stirred at 1200 rpm to2000 rpm when the condensation process is performed.
 15. An aerogelparticle, produced by following processes: performing a mixing process,wherein an alkoxysilane compound is mixed with an organic solvent toform a first mixed solution; performing a hydrolysis process to thefirst mixed solution, wherein an acid catalyst is added into the firstmixed solution to perform a hydrolysis reaction, thereby forming a sol;and performing a condensation process to the sol, wherein an alkalicatalyst is added into the sol, a hydrophobic dispersion solvent isadded and stirred during the condensation process, thereby subjectingthe sol to be gelled when it is stirred, further producing a secondmixed solution including the aerogel particle, and a particle size ofthe aerogel particle is 300 nm to 900 nm.
 16. The aerogel particles ofclaim 15, wherein the hydrophobic solvent is selected from a groupconsisting of ketone, ether, ester, aromatic and alkane.